Browsing by Subject "COMMON COLD"

Sort by: Order: Results:

Now showing items 1-13 of 13
  • Hemilä, Harri (2005)
    In their paper discussing the assessment of blinding in clinical trials, Bang et al. based their analysis on the premise that "all participants randomly guess their assignment... This is the most ideal scenario in reality". However, this premise makes an implicit assumption that the drug does not differ from placebo in any physiological effects that a person could observe subjectively, which is a very strong assumption. If a drug is truly effective, such as penicillin for pneumococcal pneumonia, both the patient and the physician can infer the treatment with high certainty by subjective observations. Thus, when the drug is truly effective, we are expecting "breaking of blindness".
  • Hemilä, Harri (2008)
    In their paper discussing the importance of double-blinding in controlled trials, Furberg and Soliman stated that one of the established and fundamental principles for avoiding the problem of bias is to keep the study participants and the investigators blinded, or masked, to the identity of the assigned interventions. As a support to this argument they described the subgroup findings of Karlowski et al.s trial, which examined the effect of vitamin C supplementation on the commoncold[2,3]. Furberg and Soliman put a great weight on the importance of double-blinding, yet they are lax on other fundamental principles of controlled trial.
  • Hemilä, Harri; Chalker, Elizabeth (2021)
    In this individual patient data meta-analysis we examined datasets of two randomized placebo-controlled trials which investigated the effect of nasal carrageenan separately on children and adults. In both trials, iota-carrageenan was administered nasally three times per day for 7 days for patients with the common cold and follow-up lasted for 21 days. We used Cox regression to estimate the effect of carrageenan on recovery rate. We also used quantile regression to calculate the effect of carrageenan on colds of differing lengths. Nasal carrageenan increased the recovery rate from all colds by 54% (95% CI 15%-105%; p = .003). The increase in recovery rate was 139% for coronavirus infections, 119% for influenza A infections, and 70% for rhinovirus infections. The mean duration of all colds in the placebo groups of the first four quintiles were 4.0, 6.8, 8.8, and 13.7 days, respectively. The fifth quintile contained patients with censored data. The 13.7-day colds were shortened by 3.8 days (28% reduction), and 8.8-day colds by 1.3 days (15% reduction). Carrageenan had no meaningful effect on shorter colds. In the placebo group, 21 patients had colds lasting over 20 days, compared with six patients in the carrageenan group, which corresponds to a 71% (p = .003) reduction in the risk of longer colds. Given that carrageenan has an effect on diverse virus groups, and effects at the clinical level on two old coronaviruses, it seems plausible that carrageenan may have an effect on COVID-19. Further research on nasal iota-carrageenan is warranted.
  • Hemilä, Harri (2011)
    Lykkesfeldt and Poulsen's review has a promising title, and in the introductory paragraph, they state that ‘over the years, it has been suggested that vitamin C be used as a remedy against many diseases as different as common colds and cancers’(1). Given their title and introduction, one would expect a discussion about randomised controlled trials (RCT) on vitamin C and the common cold. However, this topic is ignored in their review. This is an unfortunate omission because the common cold studies give interesting information on the issues that Lykkesfeldt and Poulsen discuss.
  • Hemila, Harri (2014)
    Physical activity increases oxidative stress and therefore the antioxidant effects of vitamin C administration might become evident in people undertaking vigorous exercise. Vitamin C is involved in the metabolism of histamine, prostaglandins, and cysteinyl leukotrienes, all of which appear to be mediators in the pathogenesis of exercise-induced bronchoconstriction (EIB). Three studies assessing the effect of vitamin C on patients with EIB were subjected to a meta-analysis and revealed that vitamin C reduced postexercise FEV1 decline by 48% (95% CI: 33% to 64%). The correlation between postexercise FEV1 decline and respiratory symptoms associated with exercise is poor, yet symptoms are the most relevant to patients. Five other studies examined subjects who were under short-term, heavy physical stress and revealed that vitamin C reduced the incidence of respiratory symptoms by 52% (95% CI: 36% to 65%). Another trial reported that vitamin C halved the duration of the respiratory symptoms in male adolescent competitive swimmers. Although FEV1 is the standard outcome for assessing EIB, other outcomes may provide additional information. In particular, the mean postexercise decline of FEF50 is twice the decline of FEV1. Schachter and Schlesinger (1982) reported the effect of vitamin C on exercise-induced FEF60 levels in 12 patients suffering from EIB and their data are analyzed in this paper. The postexercise FEF60 decline was greater than 60% for five participants and such a dramatic decline indicates that the absolute postexercise FEF60 level becomes an important outcome in its own right. Vitamin C increased postexercise FEF60 levels by 50% to 150% in those five participants, but had no significant effect in the other seven participants. Thus, future research on the effects of vitamin C on EIB should not be restricted to measuring only FEV1. Vitamin C is inexpensive and safe, and further study on those people who have EIB or respiratory symptoms associated with exercise is warranted.
  • Hemilä, Harri; Douglas, R M (1999)
  • Hemilä, Harri (2007)
    Moreira et al (2007) systematically reviewed the role of nutrition on exercise-induced immunodepression. However, their paper has several shortcomings. Moreira refers to Nieman’s ‘J’-curve hypothesis, which proposes that moderate exercise improves the immune system and reduces the risk of upper respiratory tract infections (URI), whereas excessive physical stress impairs the immune system and increases URI risk (Nieman, 1994). In a large cohort, we found that the risk of the common cold and pneumonia was not reduced with moderate physical activity, refuting the universal validity of the ‘J’-model (Hemila et al, 2003, 2006). There is strong evidence of positive effect of vitamin C on physically stressed people and there is no valid evidence that vitamin C would be harmful to ordinary people in doses of 1–2 g/day. Therefore, physically active people, who consider that they suffer from colds frequently, can use vitamin C, while at the same time, we hope that new trials would be carried out.
  • Hemilä, Harri; Herman, Zelek S (American College of Nutrition, 1995)
    In 1975 Thomas Chalmers analyzed the possible effect of vitamin C on the common cold by calculating the average difference in the duration of cold episodes in vitamin C and control groups in seven placebo-controlled studies. He found that episodes were 0.11 +/- 0.24 (SE) days shorter in the vitamin C groups and concluded that there was no valid evidence to indicate that vitamin C is beneficial in the treatment of the common cold. Chalmers' review has been extensively cited in scientific articles and monographs. However, other reviewers have concluded that vitamin C significantly alleviates the symptoms of the common cold. A careful analysis of Chalmers' review reveals serious shortcomings. For example, Chalmers did not consider the amount of vitamin C used in the studies and included in his meta-analysis was a study in which only 0.025-0.05 g/day of vitamin C was administered to the test subjects. For some studies Chalmers used values that are inconsistent with the original published results. Using data from the same studies, we calculated that vitamin C (1-6 g/day) decreased the duration of the cold episodes by 0.93 +/- 0.22 (SE) days; the relative decrease in the episode duration was 21%. The current notion that vitamin C has no effect on the common cold seems to be based in large part on a faulty review written two decades ago.
  • Hemilä, Harri; Louhiala, Pekka (2013)
    BACKGROUND: Pneumonia is one of the most common serious infections, causing two million deaths annually among young children in low-income countries. In high-income countries pneumonia is most significantly a problem of the elderly. OBJECTIVES: To assess the prophylactic and therapeutic effects of vitamin C on pneumonia. SEARCH METHODS: We searched CENTRAL 2013, Issue 3, MEDLINE (1950 to March week 4, 2013), EMBASE (1974 to April 2013) and Web of Science (1955 to April 2013). SELECTION CRITERIA: To assess the therapeutic effects of vitamin C, we selected placebo-controlled trials. To assess prophylactic effects, we selected controlled trials with or without a placebo. DATA COLLECTION AND ANALYSIS: Two review authors independently read the trial reports and extracted data. MAIN RESULTS: We identified three prophylactic trials which recorded 37 cases of community-acquired pneumonia in 2335 people. Only one was satisfactorily randomised, double-blind and placebo-controlled. Two trials examined military recruits and the third studied boys from "lower wage-earning classes" attending a boarding school in the UK during World War II. Each of these three trials found a statistically significant (80% or greater) reduction in pneumonia incidence in the vitamin C group. We identified two therapeutic trials involving 197 community-acquired pneumonia patients. Only one was satisfactorily randomised, double-blind and placebo-controlled. That trial studied elderly patients in the UK and found lower mortality and reduced severity in the vitamin C group; however, the benefit was restricted to the most ill patients. The other therapeutic trial studied adults with a wide age range in the former Soviet Union and found a dose-dependent reduction in the duration of pneumonia with two vitamin C doses. We identified one prophylactic trial recording 13 cases of hospital-acquired pneumonia in 37 severely burned patients; one-day administration of vitamin C had no effect on pneumonia incidence. The identified studies are clinically heterogeneous which limits their comparability. The included studies did not find adverse effects of vitamin C. AUTHORS' CONCLUSIONS: The prophylactic use of vitamin C to prevent pneumonia should be further investigated in populations who have a high incidence of pneumonia, especially if dietary vitamin C intake is low. Similarly, the therapeutic effects of vitamin C should be studied, especially in patients with low plasma vitamin C levels. The current evidence is too weak to advocate prophylactic use of vitamin C to prevent pneumonia in the general population. Nevertheless, therapeutic vitamin C supplementation may be reasonable for pneumonia patients who have low vitamin C plasma levels because its cost and risks are low.
  • Hemilä, Harri; Carr, Anitra; Chalker, Elizabeth (2021)
    Given the previous research on vitamin C, we read with great interest the report on the COVID A to Z Randomized Clinical Trial (COVID A to Z trial) which investigated the effects of 8 g/day vitamin C on the recovery from outpatient SARS-CoV-2 infection (9). However, we unfortunately found several methodological shortcomings in the trial. Here we describe our major concerns and statistical reanalysis of the findings.